Reclosers are electromechanical switches that open and close one or more phases of an electrical power line, such as between a substation and a load, such as in response to an overcurrent in the power line. As used herein, it should be understood that the term “recloser” may include various combinations of fault interrupting devices, such as reclosers, reclosing circuit breakers and the like.
In general, when an overcurrent of sufficient magnitude and duration, such as greater than a predetermined amount of current and longer than a predetermined period of time, flows through a recloser, a tripping action is initiated, circuit interrupting contacts open, and an operation counter advances one count. After a preset time delay, the circuit interrupting contacts may be automatically reclosed, thereby re-energizing the line. If the fault was temporary, such as where the fault is momentary or transient, such as due to a tree branch or animal momentarily contacting the line, and the fault was cleared before the recloser was reclosed, the recloser will remain closed and reset to its original condition after a short time delay such that the recloser is ready for the next operation. If the fault was not cleared before the recloser was reclosed the first time, the tripping action is again initiated to open the circuit interrupting contacts. The recloser will automatically reclose the contacts after a further, and typically longer, time delay.
However, not all faults that occur on electrical power lines are temporary. Rather, some faults are of a more persistent or permanent nature, such as where a storm causes an entire pole structure to fall to the ground. In response to a permanent fault, the tripping and reclosing sequence will repeat a predetermined number of times, as counted by the operation counter, until a lockout function is initiated to lock the circuit interrupting contacts open and prevent further reclosings into a permanent fault. Thus, as may be understood, the recloser will have reclosed into a permanent fault, and passed the available fault current into the circuit, several times before completing the entire reclosing cycle and locking-out to prevent further reclosing of the circuit interrupting contacts.
Examples of reclosers and their functions and operations are disclosed in U.S. Pat. No. 5,768,079, in U.S. Patent Application Publication Nos. 2004/0105204 and 2008/0266733, and in “Electric Power Distribution Handbook,” by T. A. Short (CRC Press, Boca Raton, Fla., © 2004). The disclosures of these and all other publications referenced herein are incorporated by reference in their entirety for all purposes.